Multi-component spraying systems have a multiplicity of applications, each with its specific requirements and limitation. In some prior art systems the liquid components carries a significant quantity of spray particles-away from the substrate, wastes the expensive material, creates an unclean spray area and generally requires overspray collection systems and contributes to the problem of operating such manufacturing operations safely.
In prior systems, spray nozzles have been used to atomize liquid materials which are pumped at high pressure, that is, pressures generally exceeding 30 Bar. Liquid material pumped at high pressures through such spray nozzles is forced by the hemispherical termination of the passageway to converge in its flow at and through the elongated orifice. Because of the converging flow at the orifice, the liquid material is expelled through the orifice into a planar, expanding, fan-like film which breaks into spray particles which are carried by their momentum to the article target. With viscous fluids, high pressures of 60-65 Bar are normally required. Such high operating-pressures impose a strain on system components reducing their reliability, require generally expensive components in the fluid delivery systems and contribute to the problem of operating such systems safely. Even at high pressures, however, such fan-like films, because they are formed by the convergence of the fluid, include heavy streams at the edges of the planar, fan-like film, which are referred to as “tails”. Because of the heavy stream-like flow in the tails, the spray pattern formed by these edge portions of the expanding, fan-like film includes a disproportionate quantity of material and produces a non-uniform deposit with stripes when the spray pattern is swept across a substrate by a spray gun operator. The non-uniform deposit and resulting stripes make the blending of deposited material into a film of uniform thickness virtually impossible.
One or plural components spraying methods and apparatus have been encumbered by the use of large spray guns attached to a one or plurality of hoses. Such guns were heavy, and their manipulation was resisted by a one or plurality of hoses attached at various locations to the spray gun body. These prior one or plural component systems and apparatus were, at least, commercially unattractive for industrial painting applications and, in many cases, unusable.
U.S. Pat. No. 5,178,326 discloses a spraying system for forming a coating on an article. The system disclosed in the patent provides effective and efficient mixing, atomization and deposition of plural component materials. The system follows a procedure, where a flow of compressed air is delivered to the spray gun and the combined flows of the plural component materials are mixed and formed into a fan-like film with expanding edges extending from the spray gun. The spraying system disclosed in this patent is not suitable for spraying viscous coating materials.
U.S. Pat. No. 5,645,217 discloses a spraying system for forming a coating on an article. The patent discloses a spray application system and method for a two-part, self-setting compound, comprising a source of the first part of the compound, a source of the second part of the compound, a spray device for applying the compound, a mixing assembly for intermingling the two parts of the compound, a heated hose downstream of the mixing device for delivering the compound to the spray device, a first pump or set of pumps for delivering the first part of the compound to the mixing device, and a second pump or set of pumps for delivering the second part of the compound to the mixing device. The spraying system disclosed in this patent is not suitable for spraying viscous coating materials.
US patent application no 20080075875A1 is directed to a painting system in which the temperature of the carrier fluid is kept at or brought to the required temperature at least at the moment of mixing. The spraying system disclosed in this patent is not suitable for spraying viscous coating materials.
French patent FR 1.114.098 discloses an apparatus for spraying coating viscose coating materials on surfaces, which comprising supplying of a pressure flow of coating material to a spraying means and supplying a flow of compressed air, connected to a tube piece, to assist formation of a particle spray. This patent does not envisage how coating material comprising abrasive particles may be sprayed without destroying the apparatus.
It is an object of the present invention to provide a system and method for coating a surface with a layer of viscous one or plural component coating material containing abrasive particles (e.g. SiC) with minimal wear on the system. Specifically, it is an object to provide a system and method for coating a surface with a layer of two component materials based on modified epoxy resin and loaded with abrasive ceramic particles, such as Silicium Carbide particles. Such coating material has not been possible to spray in prior art systems.
Finally it is an object of the present invention to provide a system for coating a surface with a layer of viscous one or plural component coating material, which system satisfy regulations for working on oil platforms, i.e. without risk of ignition of explosive fluids or gases. In this respect it is decisive that the system of the present invention may be used on fixed offshore platforms, in petrochemical plants where a potentially explosive atmosphere may be present. Such equipment is governed by the ATEX 95 equipment directive 94/9/EC, namely equipment and protective systems intended for use in potentially explosive atmospheres; the directive covers a large range of equipment, including equipment used on fixed offshore platforms, in petrochemical plants where a potentially explosive atmosphere may be present.